#include "zgl.h"

/*
 * image conversion
 */

void gl_convertRGB_to_5R6G5B(unsigned short *pixmap, unsigned char *rgb, int xsize, int ysize) {
    int i, n;
    unsigned char *p;

    p = rgb;
    n = xsize * ysize;
    for (i = 0;i < n; i++) {
        pixmap[i] = ((p[0] & 0xF8) << 8) | (( p[1] & 0xFC) << 3) | ((p[2] & 0xF8) >> 3);
        p+=3;
    }
}

void gl_convertRGB_to_8A8R8G8B(unsigned int *pixmap, unsigned char *rgb, int xsize, int ysize) {
    int i, n;
    unsigned char *p;

    p = rgb;
    n = xsize * ysize;
    for (i = 0; i < n; i++) {
        pixmap[i] = (((unsigned int)p[0]) << 16) |
                    (((unsigned int)p[1]) << 8) |
                    (((unsigned int)p[2]));
        p+=3;
    }
}

/*
 * linear interpolation with xf, yf normalized to 2^16
 */

#define INTERP_NORM_BITS  16
#define INTERP_NORM       (1 << INTERP_NORM_BITS)

static inline int interpolate(int v00, int v01, int v10, int xf, int yf) {
    return v00 + (((v01 - v00)*xf + (v10 - v00) * yf) >> INTERP_NORM_BITS);
}


/*
 * TODO: more accurate resampling
 */

void gl_resizeImage(unsigned char *dest, int xsize_dest, int ysize_dest, unsigned char *src, int xsize_src, int ysize_src) {
    unsigned char *pix, *pix_src;
    float x1, y1, x1inc, y1inc;
    int xi, yi, j, xf, yf, x, y;

    pix = dest;
    pix_src = src;

    x1inc = (float)(xsize_src - 1) / (float)(xsize_dest - 1);
    y1inc = (float)(ysize_src - 1) / (float)(ysize_dest - 1);

    y1 = 0;
    for (y = 0; y<ysize_dest; y++) {
        x1 = 0;
        for (x = 0; x<xsize_dest; x++) {
            xi = (int)x1;
            yi = (int)y1;
            xf = (int)((x1 - floor(x1)) * INTERP_NORM);
            yf = (int)((y1 - floor(y1)) * INTERP_NORM);

            if ((xf + yf) <= INTERP_NORM) {
                for (j = 0; j < 3; j++) {
                    pix[j] = interpolate(
                        pix_src[(yi * xsize_src + xi) * 3 + j],
                        pix_src[(yi * xsize_src + xi + 1) * 3 + j],
                        pix_src[((yi + 1) * xsize_src + xi) * 3 + j],
                        xf, yf
                    );
                }
            } else {
                xf = INTERP_NORM - xf;
                yf = INTERP_NORM - yf;
                for (j = 0; j < 3; j++) {
                    pix[j] = interpolate(
                        pix_src[((yi + 1) * xsize_src + xi + 1) * 3 + j],
                        pix_src[((yi + 1) * xsize_src + xi) * 3 + j],
                        pix_src[(yi * xsize_src + xi + 1) * 3 + j],
                        xf, yf
                    );
                }
            }

            pix += 3;
            x1 += x1inc;
        }
        y1 += y1inc;
    }
}

#define FRAC_BITS 16

/* resizing with no interlating nor nearest pixel */

void gl_resizeImageNoInterpolate(unsigned char *dest, int xsize_dest, int ysize_dest, unsigned char *src, int xsize_src, int ysize_src) {
    unsigned char *pix, *pix_src, *pix1;
    int x1, y1, x1inc, y1inc;
    int xi, yi, x, y;

    pix = dest;
    pix_src = src;

    x1inc = (int)((float)((xsize_src) << FRAC_BITS) / (float)(xsize_dest));
    y1inc = (int)((float)((ysize_src) << FRAC_BITS) / (float)(ysize_dest));

    y1 = 0;
    for (y = 0; y < ysize_dest; y++) {
        x1 = 0;
        for (x=0; x < xsize_dest; x++) {
            xi = x1 >> FRAC_BITS;
            yi = y1 >> FRAC_BITS;
            pix1 = pix_src + (yi * xsize_src + xi) * 3;

            pix[0] = pix1[0];
            pix[1] = pix1[1];
            pix[2] = pix1[2];

            pix += 3;
            x1 += x1inc;
        }
        y1 += y1inc;
    }
}
